Apparatus for stabilizing nitrocellulose



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N E K U um M G. M.

APPARATUS FOR STABILIZING NITROCELLULOSE Original Filed Feb. 27, 1935 WN NQQM N www Patented Dec. 28, 1937 UNITED STATES PATENT OFFICE APPARATUS FOR STABILIZING NITRO'- CELLULOSE Appr-@anon February 27, 1935, serial No.8,479 Renewed June 17, 1937 Y. 1 Claim.

This invention relates to an apparatus for stabilizing nitrocellulose.

I-Ieretoiorefas is well known, in the production of nitrocellulose, as nitrated cotton, it has been Vthe practice to efectfnitration of purified cellu lose, Wash-the nitratedl product almost free of acid andthen boil the product to stabilize it by the removal of residual dilute acid.

The boiling or stabilizing treatment has here- I tofore been carried out in large tubs under atmospheric pressures, the necessary heat being supplied by steam introduced into the bottom of the, tubs. Such procedure is disadvanta-geous, especially in that it is time consuming, requiring as much as fifty hours for nitrocellulose of high nitration, and hence for any substantial production a largeY amount of equipment is required With consequent high capital and maintenance cost.

.Now in accordance with this invention, there is provided a method and apparatus whereby the stabilizing treatment of nitrocellulose is eiiected with great eliiciency and with a large saving in time and consequent saving in cost.

Generally speaking, in accordance With this invention the stabilization of nitrocellulose is effected in a continuous or semi-continuous manner, at a pressure above atmospheric and at a temperature substantially above the normal boiling point of the dilute acid to be removed from the nitrocellulose. In proceeding in accordance with this invention, the primary effect upon the nitrocellulose is its stabilization and while some slight reduction in viscosity may occur, such is incidental.

The apparatus in accordance with this invention comprises, generally speaking, a passage through which the nitrocellulose is passed, the passage providingcharging and discharging zones Aand a treating zone in which the nitrocellulose, together with Water, is subjected to a hydrostatic pressure and to an elevated temperature. Means are provided for feeding nitrocellulose to the passage continuously or periodically and in a Amanner such that the nitrocellulose Will progress through the passage with continuous or intermittent movement.

Havng nowindicated in a general Way the nature and purpose of this invention, I shall proceed to a detailed description thereof with reference to the accompanying drawing, in which is illustrated a preferred form of apparatus embodying this invention, in connection with a description of which the method embodying this invention Will be described, and in which:

. Figure 1 isv a diagrammatic View of a form ofy .a U-shaped passage or tube, circular in cross section, oneY leg A of which, extending vertically, forms an inlet zone The leg A may be closed atits top, or alternatively it may be left open. 1.0 The second leg B, extending vertically, forms a discharge zone, While the base C, extending horizontally, forms a treating zone.

The charging leg or zone A is of greater height than the discharging leg or zone B, the difference .'15 in height being such as to overcome friction in the passage, so that nitrocellulose introduced into the charging zone may force previously introduced nitrocellulose through the treating zone and out of the discharging zone. 20

The charging leg or zone A is provided, at its upper end, with an inlet opening d, so positioned that nitrocellulose entering through a charging .line e, in the form of a slurry in admixture with water, will enter on a tangent to the circumference and at right angles to the axis of the charging leg or zone, as shown in Figure 2. The charging line is connected through any suitable pump, not shown, with a supply of nitrocellulose lslurry in any suitable container, not shown. 30

The treating leg or zone C is provided with steam injection nozzles f, f, positioned adjacent its inlet end and at intervals along the leg C so as to maintain desired temperature in the treating zone. The nozzles f, f, receive steam from any suitable source through a conduit g.

A cold water jet x, receiving water from any suitable source, will desirably be provided in the leg lcoolingmay be effected by the provision of a cooling jacket about the discharge end portion of the treating zone C. 'I'he cooling water may, if desired, extend into the lower end oi jacket h and discharge from the upper end.

'Ihe discharge leg or zone B is arranged to discharge into a flume 1i, by which the nitrocellulose slurry is carried to any suitable receiver, not

shown. 65

Clean-out plugs y, y are provided at appropriate points in the legs A, B and C in order to allow clean-out in the event of a jam.

In practice, using the apparatus described above, nitrocellulose slurry is introduced into the leg or zone A through inlet d, the apparatus having been previously filled with water or dilute acid. The slurry enters-the leg A'with a rotary motion, which causes the nitrocellulose to mat itself uniformly and form a loosely compacted plug, which conforms to the cross section of the leg and which moves downward through the leg or zone A and into the treating zone C, wherein it is under the hydrostatic pressure, above atmospheric, of the columns in the legs or Zones A and B and wherein it is subjected to an elevated temperature through the introduction of steam through the nozzles f.

With continued supply of slurry to the leg or zone A, it will be observed that the nitrocellulose, loosely matted, will be forced through the treating zone and up and out of the discharging leg or zone B.

In practice, however, nitrocellulose slurry is fed into the leg or zone A in increments intermittently and consequently passed through the treating zone with intermittent movement and discharged from the leg or zone B, intermittently, in increments corresponding to the increments fedV into leg A, in-order to allow the nitrocellulose in the treating zone-to remain therein a suicient time to accomplishits stabilization.

As more specifically illustrative, for example, the U-shaped passage, formed from a low carbon steel lined with a veneer of stainless steel (Plykrome) and of suitable thickness to withstand pressure, may have a diameter of twenty inches. The leg or zone A may have 4a height, from the axis of the zone C to the inlet opening d, of 45 feet, while the leg or zone B may have a height of 35 feet. The l0 foot head of leg A will overcome friction. The treating zone lC may have a length of 600 feetand steam may be introduced through nozzles f, f at say 250 F. to maintain a temperature of say about 240 F. in the treating zone. The hydrostatic pressure in the treating zone will be about 15 pounds. The temperature will be above the normal boiling point of water but below that at which water will boil under the pressure obtaining in the treating zone.

Now assuming that a nitrated cotton of about 13.40% nitrogen, such as would require about hours to stabilize by former methods, is to be treated and that the U-shaped passage has been filled with water, about 450 pounds of the nitrocotton in water (say 13 parts of Water to 1 part nitrocotton) is pumped into the charging leg A over a period of about five minutes. The nitrocotton mats and forms a plug, which drops into the treating zone, to which steam is admitted. At intervals of an hour further increments of 4,50 pounds each are pumped into the leg A, over periods of five minutes. As the increments are entered into the apparatus, previously entered increments are advanced through the reaction zone until after twelve hours an increment of 450 pounds of completely stabilized nitrocotton, cooled by the cooling jacket h to a temperature such that the water will not boil on release of the pressure, i. e. below the normal boiling point of water, is discharged from leg B into flume y', as an increment is pumped into` leg A. Thereafter an increment will be entered into and one discharged from the apparatus every hour.

It will be noted that each increment of nitrocellulose remains in the apparatus for twelve hours and since the legs or zones A and B each hold about 450 pounds of nitrocellulose, the increments will be in the reaction zone for ten hours.

From the example given, it will be observed that complete stabilization of nitrated cellulose of 13.40% nitrogen content is effected in ten hours as compared with 50 hours required heretofore. Comparable saving in time is effected in the stabilization of nitrocellulose of various nitrogen content.

The above detailed description of the carrying out of this invention involves semi-continuous procedure; however, it will be understood that the method may be readily carried out in a continuous manner by providing for a continuous supply of nitrocellulose and water to the leg A through the conduit e. Continuous supply of nitrocellulose and water will result in continuous discharge thereof. For continuous operation the apparatus described Will obviously be enlarged by lengthening the treating zone C to a Ylength with reference to the rate of feed so that the nitrocellulose will be in that zone for the requisite time, and by increasing the difference in height between the charging leg A and the discharging leg B.

It will be understood that while in the detailed description above the use of water in admixture with the nitrocellulose has been indicated, the water acts as a carrier for the nitrocellulose and that any other liquid which will act as a carrier and which is inert to the nitrocellulose under the treatment given in the zone C will be equivalent for water and is contemplated as an equivalent therefor within the scope of the claim appended hereto.

It will be understood that it is not intended that this invention shall be in any wise limited in scope by the detailed description of method and apparatus contained herein, since various and sundry modifications in details may be made within the scope of the invention.

While this invention has been described more particularly with reference to the stabilization of nitrocellulose, it will be appreciated that the method and apparatus in accordance with the invention are adapted for the treatment of any cellulose ester or ether in a fibrous condition or one which has been used in a condition approximating a fibrous condition, or other form lending them to matting in the formation of plugs through entry into the apparatus with a rotary motion as described, and that it is contemplated that in the treatment of cellulose esters and ethers they may be used for the treatment of such esters and ethers and that where adaptable the treatment of such esters and ethers is contemplated as embraced within the scope of thisy invention.

The method and apparatus in accordance with this invention is possessed of very great practical advantage in that it not only very largely reduces the time necessary for the stabilization of nitrocellulose and Where adaptable to the treatment of other cellulose esters and ethers will be found efcient, but provides for the stabilization, more particularly, of nitrocellulose with very largely increased safety in operation over stabilization in an autoclave, .as practiced by the prior art.

From the standpoint of safety, it will be noted that the surface of the liquid in the apparatus is under atmospheric pressure only so that, as will Cil be obvious, should there be any sudden evolution of gases from `any decomposition of nitrocellulose under treatment in the apparatus, such gases Will be able to escape harmlessly upon the development of only sufficient pressure to force out of the apparatus the column of liquid in one or both of the vertical legs A and Bof the apparatus. Thus, it will be obvious that on the evolution of gas from any decomposition of nitrocellulose in the apparatus, pressure Will be automatically relieved before it can rise to a point such as to disrupt the apparatus in explosive force.

In distinction, Where decomposition of nitrocellulose occurs in the autoclaves of the prior art, pressure from evolved gases is only released by a bursting of the autoclave.

No claim is made herein for the method described herein, since such forms the subject matter of an application for patent filed by me, Serial No. 750,258, led October 27, 1934.`

What I claim and desire to protect by Letters Patent is:

Apparatus for the treatment of a slurry of ibrous material suspended in a liquid comprising a substantially circular conduit of relatively large cross-section having a substantially horizontal section of great relative length and tWo relatively short substantially vertical sections of unequal length extending upwardly from the ends of said horizontal section and being connected thereto by arcuate sections having a large radius of curvature, a conduit of relatively small cross-section connected to the longer of said vertical sections at a point above the top of the shorter of said sections and opening into said section tangentially of the Wall thereof, means for heating material passing through said horizontal section and means for cooling material passing through said shorter vertical section.

MAI-ILDN G. MILLIKEN. 

